Going over the specifications for magnets on our website you will see our magnets are weight rated for a certain amount. What do those numbers really mean? Is there an ideal case where it can hold more weight or less weight? Is there a way to tell how much weight a magnet can really hold?
A Force is a Force
What we really want to do here is have a discussion of forces. What’s a force? A force is what moves your car forward or keeps you from falling on the floor when you sit on a chair. Gravity is constantly pulling down on you and forces are what keep you from falling to the center of the earth.
When you walk, the force of the floor pushes up on your feet. When you drive the force of friction between your tire and the road keeps the car moving. Without these forces nothing would ever move.
Weight is a Force
Weight is the measurement of the force of gravity pulling down you towards the center of the earth. If you drew a line through the middle of your body and pointed it at the center of the earth, that is the direction of the force of your weight.
Direction is the Key
When we talk about forces, the direction of the force is just as important as the amount of force. Why is that? And what does it have to do with magnets and weight? Magnets can generally be attached to a surface in one of two ways; they can either be attached to a horizontal surface or a vertical surface.
Sure, there is the case of an incline, but an incline is just a combination of the two we already mentioned. We are going to stick with the basics.
The Horizontal Attachment
The weights listed on our website are reflective of this case, when you have a magnet attached to a horizontal surface. This means, if you put the magnet on the metal floor, and the magnet is rated for 25 pounds of force, you would need to pull up with 25 pounds in order to get it to come free of the floor. This is called the pull force.
The Vertical Attachment: Friction is the Hidden Factor
When you attach a magnet to a vertical surface, all of those ratings go out the window. While the force that is holding the magnet to the metal is horizontal, the force of the magnet trying to fight against gravity is not the same force.
What is holding that magnet up is the force of friction between the magnet and surface. If you are attached to a smooth surface, that value goes down. If you are attached to a rough surface, that weight value goes up.
It can be hard to predict what this force, called the shear force, is going to be in the real world. It might require some trial and error work on your part to find the appropriate magnet for your need.
HS Magnets sells a variety of magnetic lifters and magnetic hooks. Make sure to know what your application is going to be and pick an appropriately rated magnet for your needs.
